2021-10-20

What happened when the asteroid that killed the dinosaurs hit the earth?

By yqqlm yqqlm

What happened when the asteroid that killed the dinosaurs hit the earth?

the most serious result of this event is the fifth extinction of life on earth: about 80% of animal species are extinct, including non bird dinosaurs. Birds, the direct descendants of mammals and dinosaurs, survived and evolved radially, becoming the dominant animals of the Cenozoic. So what happened when the asteroid collided with the earth? By studying the geology of the Chicxulub crater and the rest of the world, scientists have linked various clues to show us what happened on that terrible day and in the years that followed

researchers pointed out that the asteroid was ready to destroy the earth before hitting the earth, and finally hit the earth at the most destructive angle. The asteroid was about 12 kilometers in diameter and hit the earth’s surface at a speed of 43000 kilometers per hour, leaving a “Scar” 200 kilometers wide. More importantly, the asteroid had an included angle of 60 degrees with the horizon at the time of impact. This angle is particularly destructive and will cause the asteroid to eject a large amount of dust and aerosols into the atmosphere

the evidence found in this area supports the estimation of this angle. These evidences include the asymmetric structure of the crater, the uplift location of mantle rocks, and the unique sedimentary sequence at the core of the region, especially the lack of a unique rock type: evaporite, such as rock salt and gypsum

the violent impact evaporated the evaporite in the region, released 325 billion tons of sulfur into the atmosphere in the form of sulfur aerosol, and released 43.5 billion tons of carbon dioxide into the atmosphere

the material thrown into the atmosphere is mainly composed of gravel and sulfuric acid droplets; Sulfuric acid mainly comes from sulfate rich marine rocks evaporated during impact, namely anhydrite. Clouds containing large amounts of tiny matter form a blanket around the earth, blocking heat and light from the sun. The resulting long-term cooling has greatly changed the earth’s climate. At that time, the average temperature in the tropics dropped from 27 degrees Celsius to 5 degrees Celsius. As the sun darkened, the photosynthesis of plants weakened, and the foundations of the land and marine food chains inevitably collapsed, eventually leading to the extinction of dinosaurs and many other animals

within a few days after the asteroid impact, sulfuric acid in the air led to fatal acid rain, killing countless animals living in the upper layers of oceans, lakes and rivers

asteroid impact also triggered a huge tsunami, and shallow water waves spread in the global ocean. According to the simulation study, these waves initially reached a height of nearly 1.5 kilometers and moved at a speed of 143 kilometers per hour; Waves in other areas have also reached great heights, such as 15 meters in the Atlantic and 4 meters in the North Pacific. In the sediment records near Louisiana, the evidence of huge waves at that time is still preserved. A 3D seismic survey underground in Louisiana shows that there have been giant waves that are too long and asymmetric and up to 16 meters high, pointing to the impact site in the Gulf of Mexico

after the impact, rock debris and volcanic ash poured back to the ground, triggering a series of wildfires. The resulting smoke and volcanic ash may exacerbate the “cooling hood” effect of the atmosphere and further reduce sunlight exposure

geologists can easily estimate the time of asteroid impact when studying rock strata. There is a thin layer of iridium rich clay in the rock strata at the end of Cretaceous (66 million years ago) all over the world. Iridium is rare on earth, but it is common in space rocks. Although wildfires, tsunamis and other spectacular events can arouse people’s imagination, the most important thing is the change of the earth’s atmosphere. The terrible atmospheric cover has led to the cold years that have lasted for more than a decade

“the only way to cause mass extinction is to disturb the whole earth with something. There is direct evidence to prove this.”

Cretaceous Paleogene extinction, also known as the end of Cretaceous extinction, is the fifth and most recent mass extinction in the history of the earth. Among the five mass extinctions, the extinction degree of this event can only rank fourth. However, due to the collective extinction of non bird dinosaurs, it has become the most famous extinction event in most people’s cognition. In addition to non bird dinosaurs, most animals and plants on earth, including canglongidae, Plesiosaurus, pterosaurus, ammonite subclass and a variety of plants, have suffered extinction. Birds, the direct descendants of mammals and dinosaurs, have survived and finally become the dominant animals of the new generation

most scientists speculate that the extinction event was caused by one or more reasons, including asteroid impact event or long-term volcanic eruption. The sikxulub crater and the volcanic eruption of Deccan dark rock are close to the Cretaceous Paleogene boundary, which is considered to be the most likely cause of this extinction event. Impact events or volcanic eruptions make a lot of dust enter the atmosphere, block the sun, weaken the photosynthesis of plants, and then affect the global ecosystem. A few scientists believe that the extinction occurred slowly and was caused by the gradual change of sea level and climate

as the largest vertebrate group on the earth at that time, dinosaurs were first impacted by environmental changes, and their diversity began to decline. The suspended particles emitted by volcanoes gradually cooled and dried the global climate. The asteroid impact event eventually led to the collapse of the food chain dependent on photosynthesis, resulting in the destruction of land and marine ecosystems